Respiratory adaptations in sleep.

The current era of research into the physiology of sleep began in 1953 when Aserinsky and Kleitman (2) first described REMl sleep and its association with a characteristic EEG pattern, dreaming, and changes in autonomic nervous system activity including respiration. This important discovery demonstrated conclusively that the traditional view of sleep as a homoge­ neous state was incorrect, and indicated that preexisting observations or theories regarding sleep had to be reexamined or reinterpreted taking the stage of sleep into consideration. Accordingly much of the research in sleep physiology during the past twenty years has been directed towards a defini­ tion of the physiological differences between REM and NREM sleep and towards elucidation of the specific mechanisms and purposes that underlie the different sleep stages. In recent years these same goals have been applied increasingly to the study of respiration during sleep. To the extent that the fundamental purposes and mechanisms of sleep itself remain uncertain, so too are the purposes and mechanisms of the respiratory adaptations to sleep. Nevertheless the changes in respiration that occur in the different stages of sleep have now been studied extensively, at least in purely descrip­ tive terms. In addition, attempts have been made, although fewer in num-